[Terry_B]

I think Twitter understands that there is a much lower barrier to leaving their service for a competitor, compared to the other social services.

What data do you have in Twitter that you wouldn't be prepared to leave behind?

[robryan]

Only the graph, rebuilding your following/ followers would be a pain. Which makes sense that if they are going to be a pain about anything it is restricting access to rebuilding the graph on competing services.